Quote Originally Posted by tropicana View Post
Why not spray foam over those semi-hard foam blocks that are super pourous.... leaving a few areas for the bacteria to enter, once there they will spread and be a super-bacterial abode. Makes sense or no? Similar to below:

http://www.amazon.com/ProClear-Aquat.../dp/B0006JLUTK

Umm . . .I think some of you are forgetting what this Great Stuff Foam is originally used for - as a sealant! It is used on homes and other placed to seal out air and water. Just because you use it in a fish tank doesn't mean it stops doing what it was designed to do. It may have what looks like some small holes on the surface, but those are just like air bubble indentations. Once it dries/cures, it is not pourous to allow air/water to move through it.